rocker box breather

Wondering if anyone has changed the breather located in the rocker box.
I'm going to change the cam tensioners and while I have it opened up should I check them? Cannot find anything in the service manual about when to check or change them. How critical are they?
Any advice will be appreciated.
Thanks
Dave

They're not a required serviced item but everytime I'm in the top end I'll always replace the gaskets, valves & filter in the breathers, it's all included with the top end gasket kits. If your doing your cam tensioners using quick install push rods I wouldn't open the top end up just to do the breathers.